1. Field of the Invention
The present invention relates to a process for producing synthesis gas for the Fischer-Tropsch synthesis and a producing apparatus thereof.
Priority is claimed on Japanese Patent Application No. 2004-100941, filed Mar. 30, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, the GTL technology (Gas to Liquids) for producing liquid fuel, such as light oil and kerosene, from natural gas has attracted attention. The GTL technology consists of a step of reforming gaseous hydrocarbons to the synthesis gas of hydrogen and carbon monoxide using a reforming catalyst, and a step of obtaining converted liquefied hydrocarbons from the synthesis gas by the Fischer-Tropsch synthesis (hereafter referred to as FT synthesis).
As a method for reforming hydrocarbons such as a natural gas to synthesis gas, Japanese Unexamined Patent Application, First Publications No. 2000-104078 and No. 2002-173303 respectively disclose a process for manufacturing synthesis gas having a hydrogen/carbon monoxide ratio which is suitable for the FT synthesis, including the steps of reforming hydrocarbons, carbon dioxide and steam in the presence of a reforming catalyst at a temperature of 800 to 1000° C.
In addition, these patent documents above disclose reforming catalysts which are suitable for manufacturing synthesis gas for the FT synthesis, conditions suitable for performing the reforming reaction such as molar ratio of (steam+carbon dioxide)/carbon atoms in the hydrocarbons, the reaction temperature, and the pressure, basic constitution of a manufacturing apparatus such as a hydro-desulfurizer, and a reactor in which catalyst tubes loaded with a catalyst for reforming are installed.
However, if an attempt is made to make the production equipment larger while actually using natural gas as a raw material, in order to perform the production of the synthesis gas for the FT synthesis commercially, the following new problems which are not present appear. That is, soot (microparticles of carbon) becomes mixed in the manufactured synthesis gas for the FT synthesis, thereby enormously deteriorating the quality of the synthesis gas for the FT synthesis. In addition, a side reaction occurs in the hydro-desulfurizer, elevating temperature rapidly, such that it becomes impossible to control the temperature. Moreover, the catalyst for reforming (inlet side of the catalyst tube) is oxidized, deteriorating the activity of the catalyst.
Therefore, an object of the present invention is to provide a process for producing the synthesis gas for FT synthesis and a producing apparatus therefor, which are capable of producing the synthesis gas for FT synthesis having hydrogen/carbon monoxide molar ratio suitable for FT synthesis (1.9-2.1) and no soot mixed therein, and which can suppress the side reaction in a hydro-desulfurizer and the deterioration of the catalyst for reforming, and which are applicable to a large scale production equipment (commercial plant).